Abstract:

Feline panleukopenia virus (FPV) is a highly pathogenic threat to cats. In recent years, an FPV variant harboring an amino acid mutation at the VP2 91 site (A to S) has emerged prominently in China, however, information regarding on its pathogenicity is lacking. The aim of this study was to investigate the infection and molecular characteristics of the FPV A91S variant. F81 cells were used to isolate the FPV A91S variant, and the hemagglutination properties, pathogenicity and genomic characteristics were determined. An FPV A91S variant was successfully isolated, with a virus titer of 10^4.6 TCID₅₀·mL^-1 after viral purification. This isolate could effectively agglutinate porcine erythrocytes at pH 6.0-6.5 and temperatures of 4 ℃ and 37 ℃. When orally administered to kittens, the isolate caused a spectrum of clinical manifestations including vomiting, diarrhea, severe leukopenia, purulent discharge from the eyes, and cat death within 5 days. Gross and histopathological examinations unveiled severe hemorrhaging in the intestines and lungs. The nearly full genome sequence of this isolate was obtained, and the key amino acid residues were consistent with those of the typical FPV. In addition to the A91S mutation in VP2, three distinctive amino acid mutations (D23N, I443V and H596Q) were observed in the NS1 protein. These amino acid mutations caused the FPV A91S strains to form a discrete branch on all the evolutionary trees. This study, for the first time, investigated the hemagglutination properties and pathogenicity of the FPV A91S variant, which contribute valuable insights into the biological characteristics and genetic variations of FPV.

Key words: feline panleukopenia virus, VP2 A91 S variant, hemagglutination, pathogenicity, genetic evolution